In contrast to conventional collinear HAFs, very little is known
theoretically about Raman scattering from frustrated HAFs. This is
intriguing, since the singlet spectrum is believed to be an
essential fingerprint of such magnets. The spin \(S=1/2\)  HAF on the
triangular lattice (THAF) with NN exchange interactions is a
prominent example of strongly frustrated spin systems. It has a
ground state with non-collinear \(120^\circ \)  degree ordering of the
spins. Due to this non-collinearity of the classical ground state,
nontrivial corrections to the spin-wave spectrum
appear already to first order in \(1/S\) . It has been shown in
Refs.[1]}, [2]}, [3]} that \(1/S\)  corrections strongly modify
the form of the magnon dispersion of the triangular HAF. The resulting
dispersion turns out to be almost flat in a wide range of momenta in which
it possesses shallow local minima, "rotons", at the midpoint of the faces
of the hexagonal BZ. This differs strongly from the classical spin-wave
spectrum, which lacks such minima and flat zones. Similar results have been
obtained in series expansion studies [4]}.
